In order to enhance the cleaning efficiency of electric toothbrushes, it is desirable to move the bristle field along/about a plurality of axes. Such multi-axial movement of the bristle field achieves, inter alia, better, more intensive contact of the bristle tips to certain portions of the teeth difficult to reach otherwise. Furthermore, such multi-axial movement of the bristle field avoids that only some portions of the bristle field are moved relative to the brush head as it is the case with some prior art toothbrushes with a bristle field only rotating about an axis of rotation where the bristles close to the axis of rotation do not have much displacement, as shown in JP 2005-27762.
EP 1 093 770 B1 discloses an electric toothbrush with a rotary bristle supporting structure wherein the bristle carrier is supported in the neck of the brush head to be driven in rotary, especially oscillatory manner. The oscillating motion of the bristle carrier simultaneously induces, through a cam surface, a guided axial displacement which is a sort of rocking movement of the bristle carrier about an axis extending transverse to the toothbrush's plane of symmetry.
WO 2004-080330 discloses an electric toothbrush having a plurality of separate bristle fields which are driven to move about/along separate axes so that each bristle field has its own movement pattern. Consequently, different portions of the bristle field move into diverging directions, whereas each bristle field portion has only one axis of movement.
DE 690 31 281 T2 discloses an electric toothbrush having a pair of disc-shaped brushes with tufts which are inwardly oriented towards each other, wherein said brushes are rotated about an axis of rotation extending transverse to the longitudinal axis of the toothbrush. Between the two disc-shaped brushes, there are two bar-shaped bristle fields executing a linear oscillating movement.
Furthermore, DE 196 03 851 shows an electric toothbrush having a disc-shaped bristle carrier which is rotated about an axis of rotation extending transverse to the toothbrush's longitudinal axis and thus substantially parallel to the tufts anchored to said bristle carrier. In addition to such rotatory movement, the bristle carrier is axially oscillated along the longitudinal axis of the toothbrush. To achieve the rotatory movement and the linear movement of the bristle carrier, the drive train includes a drive shaft extending between the handle and the head of the toothbrush, which drive shaft is driven to execute a rotation about its longitudinal axis and additionally a linear oscillating movement along its longitudinal axis. Such multi-axial movement of the drive shaft necessitates a rather complicated transmission and gearing between the electric motor and the handle and the drive shaft.
EP 0 537 465 A2 shows an electric toothbrush with a pair of bristle carriers mounted to the brush head. Said bristle carriers are also rotated about a transverse axis substantially parallel to the tufts mounted to the bristle carriers, and in addition, oscillated along the longitudinal axis of the toothbrush. These two different movements of the bristle carriers are achieved with a drive shaft which executes only a linear reciprocating movement basically along the longitudinal axis of the toothbrush. More particularly, said drive shaft is connected at its one end to a rotating wheel so that the other end of the drive shaft reciprocates like the connecting rod of a combustion engine's connecting rod connecting the piston to the crankshaft. The other end of the drive shaft is connected to the bristle carriers to move such bristle carriers along the toothbrush's longitudinal axis in a reciprocating manner. To additionally provide for rotation of said bristle carriers, the bristle carriers are provided with pinions in engagement with a toothed rack mounted to the brush head. Such transmission is rather complicated and makes the brush head rather bulky.
It is a desire to provide an improved electric toothbrush and an improved brush head for such toothbrush which avoid disadvantages of the prior art and provide improvement thereof. Particularly it is a desire to provide a multi-axial bristle carrier movement for better cleaning efficiency without complicated transmission and gearing in the drive train and achieving a slim, space saving configuration.